How could I install the downloaded products?
Firstly, you will receive a zip file, which you have to extract using zip software that is freely available allover Internet.
Subsequently, you will receive a video file (in mp4 or avi format). Synchronize your iPhone on iTunes and drag that file to your music & video files to copy it to your iPhone. Then, you could find it in your iPhone: choose iPod, category: Video.
But first, make sure that you have checked the checkbox “Manually manage your music and videos” on your iTunes..then you can drag the product into your iPhone.

problem is i dont get what it means "Synchronize your iPhone on iTunes and drag that file to your music & video files to copy it to your iPhone. Then, you could find it in your iPhone: choose iPod, category: Video."